Widespread resistance to long-used drugs and to newer quinoline-based drugs has prompted the need to better understand malaria parasite biology and pathogenesis. Egress from the infected RBCs by the invasive stage of the malaria parasite is a fundamental step in the pathogenesis of malaria of which little is known. The cyclical waves of fever and chills associated with malaria result from the synchronous rupture of infected red blood cells releasing numerous parasites into the bloodstream for invading fresh RBCs. The clinical importance of this phase of malaria underscores the importance to understand the biology of egress step, along with the need for better therapeutic control of severe malaria. Before infecting new erythrocytes, the merozoites have to exit host cell to get into the bloodstream. While within the infected RBCs, the developing merozoite is surrounded by erythrocyte membrane and parasitophorous vacuolar membrane (PVM), both of which must be broken down for egress. Knowledge about the mechanism of egress is scarce, but it is thought that the proteases are involved in this step and therefore, much of the work on egress has so far focused on the search and identification of proteases that can breakdown the PVM and RBC membrane. Here we plan to utilize forward and reverse genetics approach to address the molecular mechanism(s) of egress. In addition, we will assess the involvement of calcium signaling pathways in regulation of protease activation. PUBLIC HEALTH RELEVANCE: Malaria is caused by a parasite transmitted by anopheline mosquitoes, and results in over 2 million deaths and 500 million infections each year in developing countries around the world. Furthermore, over two billion people are at risk of getting infected with malaria. Currently, there is no commercially available malaria vaccine and parasite resistance to the cheap, yet effective, anti-malarials is rapidly increasing. The goal of this application is to study the genes and pathways involved in promoting parasite exit from the red blood cell. Understanding the biology of this important step in infection will provide new strategies for treatment of malaria and development of anti-malarial vaccine.